The invention discloses a building roof rainwater collection treatment device. The building roof rainwater collection treatment device comprises a roof, and rainwater diversion trenches are formed in the roof; rainwater drainage pipes are fixedly connected under the ends, close to an eave, of the rainwater diversion trenches; the rainwater drainage pipes are inserted into a ground surface; a plurality of rainwater drainage pipe placing grooves are formed under the ground surface; a reservoir is arranged under the rainwater drainage pipes; an abandoning device is arranged on the side surface of the reservoir; the abandoning device is composed of an abandoning box, a water inlet formed in the abandoning box, a water outlet formed in the abandoning box, a blowdown hole formed in the abandoning box, and an abandoning device mounted in the abandoning box; a filter device is arranged on the side surface of the abandoning device; the filter device is composed of an aeration oxygenation device, a water screening device and an automatic flushing device; a water storage tank is arranged on the side surface of the filter device; and the water storage tank communicates with a diversion pipe through a water conveying pipeline. The building roof rainwater collection treatment device has the benefits of simple structure and high practicability.